The goal of this SBIR is to create a novel phototherapeutic light delivery device which will advance the standard of care for the prevention and treatment of Oral Mucositis (OM). OM is one of the most common and highly significant toxicities of cancer therapy. Approximately 450,000 patients are affected by OM in the United States each year. OM is an extremely painful condition which breaks down the lining of the mouth and is associated with increased treatment breaks, increased 100-day mortality and a considerable increase in healthcare costs. The standard of care for patients with OM is mainly palliative, aiming to reduce pain, inflammation, and risk of infection. A new, proven, and powerful approach for both treatment and prevention of OM is Phototherapy (PT). Near-Infrared light increases the production of ATP which protects the mucosa from cell death. No reported side effects are observed from using phototherapy for the treatment of OM. Current barriers to the use of phototherapy include the cost of laser equipment, labor intensiveness, inter-operator variability, and inconsistent light penetration. Lumitex PT is developing a flexible, biocompatible silicone light guide to irradiate the entire oral mucosa with therapeutic light. The key innovation is the simultaneous irradiation of the entire oral cavity with minimal clinical supervision while significantly increasing patient comfort and compliance. Our light delivery technology can be integrated into a mouthpiece that safely delivers 4-6 J/cm2 of NIR light directly to the oral mucosa in a tolerable period of time and can demonstrate compliance. To address this hypothesis we created these aims: 1. Construction and optimization of a device utilizing light guide technology to deliver phototherapeutic light to the entire oral mucosa simultaneously. Manufacturing a device that meets the output and safety requirements detailed in this proposal will complete this aim. 2. Demonstration of patient compliance and safety in a controlled clinical environment. A pilot study will be comprised of head and neck cancer patients undergoing radiation while receiving phototherapeutic treatment under conditions mimicking expected end use. The device will be evaluated based on fitness for intended use and patient safety. Upon completion of Phase I, we will successfully have developed a phototherapeutic mouthpiece capable of delivering the required light dosage in an effective, controlled manner. During Phase II we will develop a manufacturable, sterilizable, cost-effective iteration for commercialization and prove its clinical efficacy. Our long-term goal is to create a home-based device for all patients at risk for developing Oral Mucositis, allowing the clinician to control dosage and the patient to self- administer.